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Synchronization NI PXIe-5122 with NI PXIe-6356



I'm trying to synchronize NI PXIe 5122 (100 MS/s, 14-Bit Digitizer/Oscilloscope) with NI PXIe-6356 (Simultaneous X Series Data Acquisition). Does anyone have any example that can be useful (about synchronization NI PXIe 5122 with some DAQmx card, such as NI PXIe 6356) ?




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Hi blaza!


I saw, that you opened another thread with the same topic here: http://forums.ni.com/t5/LabVIEW/Synchronization-NI-PXIe-5122-with-NI-PXIe-6356/m-p/2196986#M703735

I think it's enough to discuss this issue in this topic, so I will post there the link of this topic.

First of all let's collect some information about the hw:

Regarding to the


- 15th page of the specification of PXIe 5122 (http://www.ni.com/pdf/manuals/371172m.pdf), it has a PLL Reference Clock source

   => at PXI_CLK10 (backplane connector) 

   => at CLK IN (front panel SMB connector)

   Both inputs hhav a frequency range from 1 MHz to 20 MHz in 1 MHz increments. The default is 10 MHz frequency. 


- 8th page of the specification of PXIe 6536 (http://www.ni.com/pdf/manuals/370082b.pdf), it can use the

    => PXIe_CLK100 (100 MHz)

    => PXIe_DSTAR<A, B> (10, 20, 100 MHz)
    => PXI_STAR (10, 20 MHz) (The PXI star trigger is a feature implemented on National Instruments PXI chassis: http://zone.ni.com/reference/en-XX/help/370524L-01/nisignal_generators_help/integration_pxi_star_tri...
    => PXI_TRIG <0..7> (10, 20 MHz)
    => PFI <0..15> (10, 20 MHz)


as reference clock locking frequency.


There is an important information, that you have to know: 
X series devices can only PLL to the 100MHz clock on the PXI Backplane (PXIe_CLK100) when trying to synchronize multiple devices.

For more information please visit: http://digital.ni.com/public.nsf/allkb/A254EB07087CCC83862576EB00515C24?OpenDocument

If you go throguh the X series manual on the page 7-52, you wil find the following:


Depending on how you configure your device, X Series devices use one of three synchronization methods:
• 100 MHz Source Mode
• External Source Greater than 25 MHz
• External or Internal Source Less than 25 MHz

So my first question is what kind of chassis do you have? 
This is important, because as you see above, PXIe 5122 needs a 10 MHz reference clock to PLL, but the PXI 6536 needs a 100 MHz reference.
For example if you have a PXI 1075, that has 3 system reference clcok signals, whose relationship is described in the following figure:
If a 10 MHz clock is present at the Rear Chassis Panel 10 MHz REF IN, PXI_CLK10, PXIe_CLK100 are phase-locked to Rear Chassis Panel—10 MHz REF IN. So you could use the PXI_CLK10 for the 5122 and the PXIe_CLK100 for the 6536 as PLL reference. The same is true if you have a 10 MHz clock present in the sys. timing slot. 
Soruce: NI PXIe-1075 User Manual, page:1-11 and 1-12: http://www.ni.com/pdf/manuals/372537b.pdf
If the 2 devices have proper references to PLL to, you have to export the start event/trigger from the DAQmx card and use that as the source of the Start Trigger on the digitizer. 
You need this, because it is harder to synchronize a digitizer when acquiring continuously because you need a common starting point on both devices in order for them to start sampling at the same time. 
And the digitizer doesn't use a normal reference trigger by default when performing continuous sampling. However, you can use an Acquisition Start Trigger signal on a digitizer to tell it when to begin sampling.
To configure a Start Trigger on the digitizer, you will need to use an niScope property node found under Synchronization » Start Trigger (Acq. Arm) » Source
Since the digitizer will be waiting for the exported signal from the DAQ card, you will want to initiate the digitizer first, then start the DAQ card, that will produce the start signal for the digitizer.
To make the operations sequential, you will probably need to route your error wires between the niScope and DAQmx functions so that proper timing and data flow is maintained. 
Also, keep in mind that because the digitizer is sampling at a much higher rate than the DAQ card, there may be some small differences between the phase due to the delay of exporting the start trigger.
Here is a useful article how to generate a trigger with your DAQ device on the PXI backplane: http://digital.ni.com/public.nsf/allkb/925A7B2946E6E769862571110027A316?OpenDocument
An other method for synchronization:
Export a down divided sample clock from the 5122 to use it as the sample clock source on the X Series card. 
This will only work if you can sample on the X Series device at a rate which is an integer divide down from the 5122's 100 MS/s rate. 
A usefull article about PFI Lines (X Series. M Series, E Series): http://digital.ni.com/public.nsf/allkb/14F20D79C649F8CD86256FBE005C2BC4
In this case though, you would start the DAQmx device first, and then as soon as the digitizer initiates its acquisition, the sample clock will be sent to the X Series DAQ device and it will also start sampling. 
Of course, as before, there will be some small difference between the cards due to the propagation delay of exporting the sample clock to the other card (the digitizer will already be sampling while the clock gets sent to the DAQ device).
I suggest you to search for examples in the example finder, (Help >> Find Exmaples...) using the keywords: niscope, daqmx, synchronization to find practical solutions, but the principle should be as I wrote above.
Please don't hesitate to post your questions.
Best regards,
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Hi blaza!


Could yo go through on my reply?


Did it help?


Do you have any question?


Please do not hesitate to post them.



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I was not able to respond earlier. Your answer was useful. I solved the problem few days ago. Thanks!


Best regards!

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